The present invention relates to a device or arrangement for transmitting electrical signals or energy, respectively, between several units mobile relative to each other.
For the sake of a clear description, the present patent document does not discriminate between the transmission of units mobile relative to each other and a stationary unit with units mobile relative to it because this is only a question of local reference and does not take any influence on the mode of operation of the invention. Moreover, a more detailed distinction between the transmission of signals and energy is not made as the mechanisms of operation are the same in this respect. Furthermore, the term xe2x80x9cpath of a movementxe2x80x9d may correspond to a straight line, a circle or any other curve.
With units mobile along a linear path, such as hoisting and conveying installations and also in the case of rotatable units such as radar installations or even computer tomographs, it is necessary to transmit electrical signals or energy between units mobile relative to each other. For the transmission of signals both contacting and non-contacting methods are known. U.S. Pat. No. 5,208,581 discloses a method that permits the transmission of signals in a contacting manner, using a closed conductor. This method displays two decisive disadvantages. On the one hand, it is applicable only for closed arrangements in rotational symmetry and does hence not provide a solution for linear transmission systems such as those required for crane installations. On the other hand, this system displays very poor high-frequency properties in the event of signal feed from a mobile unit into the signal paths. The problem here resides in the aspect that a termination must be coupled at a position diametrically opposite to the feeding site via a second sliding-contact arrangement. The signal transmission operates perfectly only when both the feed coupler and the termination are appropriately coupled. In practical operation, this can be achieved with very great difficulties only when the usual sliding-contact arrangements such as gold spring wire or silver graphite carbons are used. The reason for this resides in the aspect that such contact systems have a contact resistance that may have a broadband noise character over a bandwidth of up to several megahertz. When now a series circuit (feeding site and termination) of two of such contact systems is required for a perfect function of the transmission system a low-noise transmission can be realized only with a very high expenditure. In this respect, non-contacting transmission techniques entail advantages, such as those described in the U.S. Pat. No. 5,530,422 and in the German patent specification DE 197 00 110. The first one of these transmission techniques uses a strip line for transmission whilst the second one of these transmission techniques operates on a conductor structure composed of a plurality of discrete dummy elements. This offers the advantages of very high noise suppression. In distinction from the conductor system mentioned first, both conductor systems are connected by their ends to form a closed ring. They are open and may hence be matched with any trajectory whatsoever. A respective termination element is provided on both ends of these conductor structures to form a reflection-free termination. The signals are fed invariably at a suitable site into the conductor structure. Hence, the signals are always transmitted from the conductor structure to a unit disposed for movement relative to the conductor structure. This systems presents, however, serious disadvantages in various applications. When, for instance, in the case of a linear transmission the signal transmission from mobile crane installations to a stationary unit is desired, an antenna element must be mounted on that mobile crane installation, which element covers the entire length of the displacement path. This means that an antenna carrier of 50 m in length, for example, must be mounted at the bottom of the crane installation. In other fields of application, e.g. in computer tomographs, the conductor structure is applied on a mechanical slip ring that rotates together with the rotating part. Hence, data transmission from the rotating part to the stationary part is possible without any problems whilst a transmission in the opposite direction requires an additional ring for receiving a stationary conductor structure. Specifically in the field of computer tomographs, this cannot be realized for reasons of costs.
The present invention is based on the problem of providing a device for the non-contacting transmission of electrical signals, which permits a transmission from a mobile unit to a conductor structure simultaneously in both directions.
For the signal transmission between two parts mobile relative to each other and disposed along any trajectory whatsoever, a symmetrical conductor structure is used which is operated on a differential signal and which is terminated in a reflection-free manner on both ends. In the event of a unidirectional transmission, the signals are fed into the conductor structure through a coupling unit disposed for mobility relative to it. This coupling unit is designed as a conductor structure that is so designed that it can couple signals into the first conductor structure by inductive or capacitive means. The signals are decoupled through a decoupling element mounted in a stationary manner relative to the conductor structure.
A particularly expedient embodiment of the arrangement is so designed that signals may be transmitted in both directions. The signal transmission direction from the conductor structure to an element mobile relative to the structure will be referred to as first transmission direction whilst the opposite direction will be referred to as the second transmission direction. The signal transmission in the first direction takes place on principle by feeding the transmission signal at an invariably predetermined site into the conductor structure. In the event of rotatable arrangements it is sensible to dispose the feeding site in the centre of the conductor structure, i.e. at the site that is equidistant from both ends. Hence, the delay times of the signal running to both ends of the conductor structure are of the same length and correspondingly the phase shift is zero. This results in a continuous phase development without discontinuities in the passage over the ends of the conductors. The signal transmission in the second direction takes place in the aforedescribed manner from the mobile unit to the conductor structure.
In a particularly simple embodiment of the arrangement, the receiver of the second direction can be mounted on the conductor structure on the same coupling site as the transmitter for the first direction. As a matter of fact, with this type of configuration, however, only a half-duplex operation is possible, which means that data can be transmitted in one of the two directions only by the same point of time.
Another expedient embodiment of the invention consists in the provision that directional couplers are used to separate signals of a first and a second data transmission means from each other. As a result, the simultaneous transmission is possible in both directions (full duplex operation).
In a further expedient embodiment of the invention, at least one of the two signals is modulated additionally onto a carrier for the first or the second direction. When this carrier is selected beyond the transmission range of the respectively other signal a simple separation of the two signals is also possible in duplex operation.
According to another embodiment of the arrangement, at least one directional coupler is integrated into the substrate of the conductor structure for decoupling the signals in a directionally selective manner.
A further embodiment of the invention provides for at least one directional coupler for directionally decoupling of the signals, which is integrated into the carrier of the conductor structure.
In a further embodiment of the invention, at least one directional coupler for directional separation of the signals is integrated into the feeder line leading to the coupling point of the conductor structure.
In another embodiment of the invention, the signals are coupled into and decoupled out from the conductor structure by units mobile relative to the structure. Hence, signal transmission is possible between units moving at different relative speeds.
Another embodiment provides for an additional invariable coupling and decoupling of signals on the conductor structure.
According to a further expedient embodiment of the invention, at least one coupler unit mobile relative to the conductor structure is realised as directional coupler. Hence, signals can be coupled in and decoupled out as a function of the direction. This permits a better separation of transmitted and received signals.
In another expedient embodiment of the invention, a respective receiver is undetachably connected on both ends of the conductor structure. Additionally, at least two mobile transmitter units are provided which are designed as directional couplers. These transmitter units are so disposed that the first transmitter unit transmits the signals in a direction towards the first receiver associated with it. The second transmitter unit is so arranged that it will transmit its signals in the opposite direction towards the receiver associated with it.
In a further advantageous embodiment of the invention, a transmitter for the first signal transmission direction as well as a receiver for the second signal transmission direction are coupled on at least one end of the conductor structure by means of a directional coupler. This directional coupler may be designed to comprise conducting elements or even discrete components such as transducers in correspondence with prior art. A receiver element designed as directional coupler is provided for receiving the signals from the first transmission direction. The transmitted signals are transmitted or coupled into the second transmission direction via a second coupler unit mobile relative to the conductor structure. In order to avoid over-coupling of the signals from the mobile transmitter to the mobile receiver it is necessary that the transmitter is located on that side of the receiver, which is turned away from the transmitter associated with the first signal transmission direction.
In another expedient embodiment of the invention at least one transmitter or receiver is coupled fixedly to the conductor structure via directional couplers and a mobile transmitter is provided, which is provided with a coupling element designed as directional coupler. The mobile receiver unit may be designed here without any directional selection when it is located on that side of the mobile transmitter, which is turned away from that end of the conductor structure, which is connected to the receiver of the second signal transmission direction.
In a further expedient embodiment of the invention, the mobile coupling elements for the mobile transmitter and for the mobile receiver are designed as directional couplers in the case of a fixed contact with the conductor structure with a transmitter and a receiver via directional couplers.